1. Field of the Invention
The present invention relates to a recording apparatus and a recording method.
2. Description of the Related Art
It is conventionally known that an inkjet recording apparatus has various advantages such as ability to record a high-quality image at high speed, low running costs, and ability to perform quiet recording. Many inkjet recording apparatuses record an image using inks containing pigments. An inkjet recording apparatus using pigment inks is used also to record images for a poster and a photograph, and has been required to record a higher-quality image in recent years.
When recording of the images is performed using pigment inks, there is a known problem in the image clarity of the recorded material. The image clarity is an indicator for determining whether or not a recorded image appears vividly when light has been projected onto the recorded image. The image clarity is known as one indicator for evaluating glossiness. It is known that the smoother the image obtained on the surface of a recording medium, the higher the image clarity, and that the more uneven the image, the lower the image clarity. Pigment inks are fixed while depositing on the surface of a recording medium in a laminated manner, whereas dye inks are fixed while penetrating into a recording medium. Thus, pigment inks are more likely to increase the unevenness of the surface of an image than dye inks, and therefore it is difficult to obtain a high image clarity. The image clarity can be measured according to a method described in JIS-K7105.
To reduce the deterioration of the glossiness resulting from the deterioration of the image clarity due to the use of pigment inks, Japanese Patent Application Laid-Open No. 2008-162095 discusses a method of acquiring the gloss characteristic value of an image to be recorded from the gloss characteristic value specific to each pigment ink. According to the method, inks that cause the deterioration of the glossiness are combined, the degree of dot dispersion is reduced and the dots are joined to record an image. The joined dots form a single large dot on a recording medium. The surface of the large dot is smoother than the surface formed when the same number of dots as the joined dots are imparted in different recording scans. This can reduce the deterioration of the image clarity.
The method discussed in the Japanese Patent Application Laid-Open No. 2008-162095, however, performs recording by forming a large dot, and therefore results in forming an image having a granular quality.
Further, as a result of studies, the inventors have found that by the method discussed in the Japanese Patent Application Laid-Open No. 2008-162095, the gloss characteristic value of an image is determined based on the gloss characteristics of each ink to be used, and therefore a sufficient image clarity may not be in some cases obtained.
This problem is described in detail below.
FIGS. 1A, 1B, and 1C are cross-sectional views of the state of the surface of a recording medium when a first ink has been applied and fixed on the recording medium, and then a second ink different from the first ink is applied.
The first and second inks have the relationship such that the second ink penetrating into the layer of the first ink fixed on the medium has a smaller permeability than a permeability of the first ink penetrating into the layer of the second ink fixed on the medium. Largeness of the permeability varies depending on various factors, but is largely controlled particularly by the physicochemical properties of the first ink applied under the second ink. In the specification, the power of an ink applied underneath that inhibits the penetration of an ink applied above is referred to as the penetration inhibiting power of the ink applied underneath.
FIG. 1A illustrates the state of dots 1102, which are formed after the first ink has been applied onto a recording medium 1101 and fixed. The first ink produces a color owing to a pigment 1103 (a color material component) which has become deposited on the recording medium 1101. Further, the dots 1102 of the fixed first ink contain not only the pigment 1103 but also a resin component and a solvent component, although in small amounts.
FIG. 1B illustrates the state of a dot 1106, which is formed by the second ink immediately after the second ink has been applied on top of the dots 1102 of the first ink in a laminated manner. If the permeability of the second ink penetrating into the first ink is small, it is difficult for a solvent component contained in the second ink, such as moisture and solvent, to penetrate into the dots 1102 of the first ink. Accordingly, the solvent component that cannot penetrate into the dots has a strong tendency to spread in directions parallel to the surface of the recording medium 1101.
FIG. 1C illustrates the state of the dot 1106 of the second ink fixed on the dots 1102 of the first ink. The dot 1106 of the second ink is formed to spread more in directions parallel to the recording medium 1101, as compared to a state immediately after the application of the second ink as illustrated in FIG. 1B. Further, until the second ink has been fixed, the solvent component flows in directions parallel to the surface of the recording medium 1101. Thus, a pigment 1107 and a resin component are also influenced by the flow and tend to concentrate in an end portion 1110 of the dot 1106. As a result, in the obtained image, an area corresponding to the end portion 1110 of the dot 1106 of the second ink becomes more bulky than other areas.
FIGS. 2A to 2B are diagrams sequentially illustrating the state of the surface of a recording medium when first and second inks have been applied to the recording medium by four recording scans without setting a particular order of application of the first and second inks.
FIG. 2A illustrates the surface of the recording medium after a first recording scan. Specifically, a dot 603 of the first ink and a dot 602 of the second ink are formed on a recording medium 601. At this time, the recording duty is low, and therefore, individual dots are not in contact with each other and are fixed in isolation.
FIG. 2B illustrates the state after a second recording scan. At this time, areas appear where two dots overlap with each other. The first ink has a strong penetration inhibiting power, and therefore, the ink applied at a position overlapping with a dot 605 of the first ink formed by the first recording scan flows to the recording medium 601. This forms an ink dot 606 biased in the direction of the recording medium 601. Further, due to this flow of the ink, also a pigment and a resin component to be deposited on the surface of the recording medium 601 after fixing move in the direction of the recording medium 601. Thus, an end portion 604 of the dot 606 tends to become bulky. As described above, this phenomenon is caused mainly by the strength of the penetration inhibiting power of the ink applied underneath. Thus, regardless whether the first or second ink has been applied on top of the dot 605 of the first ink, this phenomenon occurs.
Thus, the more the areas in the recording medium where an ink is applied on top of a dot of the already fixed first ink, the more the bulky areas. The occurrence of such local bulkiness results in a low smoothness of the surface of an image to be ultimately obtained. Thus, a sufficient image clarity may not be obtained.
The above problem of the image clarity notably arises, particularly when recording is performed by using glossy paper. The glossy paper is a recording medium on the surface of which an absorbing layer for absorbing ink is formed.